The prior art is replete with electronic devices and components designed for high frequency data communication applications. A common practical application for such devices and components is cellular telephony systems. In this regard, the need for component integration will increase as module sizes decrease for high performance cellular phones with advanced features. Cellular phone radio transmitters use several passive components for functions such as filtering, impedance matching, and switching. Several of these components can be integrated to improve module parameter control and cost. A harmonic filter is used for signal selectivity over radio bands, while an RF coupler is used for signal level sensing and control. For example, an RF coupler may be used to couple an RF signal in a transmit path to a detector for signal power level control. In conventional applications, an RF coupler and a harmonic filter are two separate components, each having a physical size of approximately one square millimeter. In such applications, the use of distinct components necessarily adds to the overall footprint of the module, while increasing manufacturing and assembly cost. In addition, the use of a separate RF coupler requires different device fabrication processes, which in turn may lead to unpredictable coupling performance, impedance matching, and other operating characteristics.
Some integrated RF coupler designs may be highly sensitive to alignment tolerances associated with the photolithography process utilized to create the RF device. Other integrated RF coupler designs may rely on capacitive coupling effects, which increase the amount of coupling at the cost of directivity. Such loss of directivity may be undesirable, particularly for directional RF couplers.